The broad, long-term objective of the proposed research is to further understanding of the behavioral and physiological processes underlying the development and control of chronic muscle pain in the region of the face and temporomandibular joint. While considerable advances in understanding the mechanisms associated with acute, cutaneous pain have occurred, less is known about the factors influencing chronic pain from musculoskeletal structures. The proposed research will address the behavioral and physiological factors differentiating chronic masticatory muscle pain patients from healthy, matched controls during rest and laboratory challenge. At rest, it is expected that chronic muscle pain patients will report more anxiety than the matched normal controls. It is also hypothesized that chronic muscle pain patients will display greater emotional and physiological responsivity than the normal controls during laboratory challenges. Finally, it is predicted that chronic muscle pain patients will have lower pain thresholds and greater pain sensitivity when undergoing acute pain stimulation as compared to normal controls. This research effort is directed towards clarifying physiological and psychological factors influencing the pathogenesis of muscle pain in the temporomandibular region. Such knowledge would contribute to the development of more effective treatment methods for managing the very common symptoms associated with temporomandibular disorders.